Most car users selected to travel short distance about 100 - 300 km (Over 50%) from the origin and the number of car users gradually decrease after distance 300 km and increasing again at distance about 600 – 800 km in ST and 900 – 1,000 km in HY. Figure 12 showed distance which the number of car users increase again, in the range of 600 – 800 km and distance 900 – 1,000 km which is the distance between ST to Bangkok and HY to Bangkok, respectively. Consideration of the relationship between trip purposes and distance of ST show that for short distance, the main purpose of respondents was travelling for leisure and for long distance was travel for business. In HY, similarly for short distance but for long distance number of respondents selected same purpose about 10% of respondents in each purpose.
The 2010 OTP study of Thailand Master Plan for Transport and Traffic Development [22] has set the target for growth and mode share as follows: intercity public transport is to increase from 41% to 46% over the decade of the plan; reduction in private car use from 59% to 54%; rail ridership is to be increased to 35% over the 12-year span (2007-2018). However, the government’s emphasis on developing the rail mode, in particular, the double-track and the high-speed systems can be seen that the planned express train (120 km/h on double track) will have a competitive edge over the bus and private car modes at travel distances of 200 km or longer. The HSR (250 km/h) will rival the flying mode at distances about 600 km. Given the prospects of such improvement, plus appropriate upgrades on the intercity rail systems, passengers will be accorded a better array of travel options which will help to discourage private car use and encourage their switching to the public modes, especially for travel distances over 200 km.